Preparation of Dense BaTiO 3 Ceramics with Submicrometer Grains by Spark Plasma Sintering

Dense BaTiO 3 ceramics consisting of submicrometer grains were prepared using the spark plasma sintering (SPS) method. Hydrothermally prepared BaTiO 3 (0.1 and 0.5 µm) was used as starting powders. The powders were densified to more than similar/congruent95% of the theoretical X‐ray density by the SPS process. The average grain size of the SPS pellets was less than similar/congruent1 µm, even by sintering at 1000‐1200°C, because of the short sintering period (5 min). Cubic‐phase BaTiO 3 coexisted with tetragonal BaTiO 3 at room temperature in the SPS pellets, even when well‐defined tetragonal‐phase BaTiO 3 powder was sintered at 1100° and 1200°C and annealed at 1000°C, signifying that the SPS process is effective for stabilizing metastable cubic phase. The measured permittivity was similar/congruent7000 at 1 kHz at room temperature for samples sintered at 1100°C and showed almost no dependence on frequency within similar/congruent10 0 ‐10 6 Hz; the permittivity at 1 MHz was 95% of that at 1 kHz.